Many types of abrasive wheels are known in the prior art. A type of abrasive wheel proven to have exceptional grinding properties is the type made with abrasive grains embedded in a plastic binder. Common plastic binders include materials such as polyurethanes and epoxies.
In the past, abrasive wheels of a plastic type have been formed by mixing together the liquid binder, abrasive grains and other materials such as fillers. Once the materials are mixed they are poured into a mold. The mixture is then heated in the mold to cure the binder and form a solid wheel. The wheel is then removed from the mold and a skin of abrasive free binder that typically forms at the open surface of the mold is removed. Once the skin is removed, the wheel is suitable for use.
The problem with the prior art approach of making abrasive wheels is that they tend to be filled with air bubbles in the interior. This characteristic is referred to as "porosity". Porosity is undesirable in a grinding wheel because it tends to score the material being ground. Porosity also tends to cause imbalance in the wheel.
It is believed that the characteristic of porosity occurs because small amounts of air are introduced during the mixing and pouring processes. The tiny air bubbles expand during curing to form significantly larger pockets inside the wheel. Various approaches have been tried over the years to eliminate porosity, however the condition has persisted in commercially available wheels.
Thus, there exists a need for a method for manufacturing abrasive wheels that reduces porosity while providing improved wheel balance and grinding characteristics.